This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background Utilization of neural stem/progenitor cells (NSPCs) is regarded as a possible therapeutic tool for promoting brain recovery following stroke. We had demonstrated that NSPCs exhibit a strong ability to support endothelial cell survival, morphogenesis and angiogenesis following ischemia. Our study of the molecular mechanisms of NSPC-mediated protection, lead us to a major discovery that the vasculotrophic effect of NSPCs is mediated via activation of the HIF-1a/VEGF pathway. Hypoxia-inducible factor-1 alpha subunit (HIF-1a) is a transcriptional activator mediating adaptive cellular response to hypoxia. Normally degraded in most cell types and tissues, HIF-1a becomes stable and transcriptionally active under conditions of hypoxia. In contrast, we found that HIF-1a is constitutively expressed in NSPCs, regulating expression and pro-angiogenic signaling of the vascular endothelial growth factor (VEGF). These findings lead to our central hypothesis that neural stem cells provide protection for brain endothelial cells and support functional remodeling of the brain vasculature following ischemia. We propose that vasculotrophic properties of NSPCs are governed by transcription factor HIF-1[unreadable], both under normal conditions and following hypoxia. Aims To address our hypothesis, we proposed to study the role of HIF-1[unreadable] signaling in NSPC function and to determine the effects of NSPC-specific HIF-1[unreadable] gene deletion on stroke-induced angiogenesis. Our main approach is to study functional changes in the brain vasculature following experimental focal ischemia, using magnetic resonance imaging (MRI) and superparamagnetic nanoparticles (SPIOs) as a contrast agent. HIF-1a conditional knockout mouse and/or NSPC-transplanted rat model will be used in these studies. Our proposed methods include stem cell isolation, expansion, differentiation and transplantation, direct contact and indirect in vitro cell co-cultures, immunofluorescence confocal microscopy, various biochemical and cell biology methods, HIF-1a gene silencing utilizing conditional knockout animals and shRNAi, as well as magnetic resonance imaging (MRI) using superparamagnetic nanoparticles (SPIOs).